Water vapor or water is injected into the combustion chamber of the gas turbine plant for reducing the NOx emissions in the turbine exhaust gas. The flame temperature is consequently lowered and thus low NOx emissions are achieved.
Furthermore, the technique of injecting water or water vapor is also utilized to achieve an increase in the performance of the gas turbine. The specific heat capacity of the hot gas is increased by the addition of water or water vapor, such that a greater difference in enthalpy is present in the turbine. The mass flux in the gas turbine is increased by the supply of water or water vapor, as a result of which the performance is again increased with the further addition of fuel. Accompanying the increase in performance is the improvement in the efficiency of the gas turbine.
Injecting water or water vapor directly through the fuel nozzles of the combustion chamber is well known. However, because of the narrow space conditions in the combustion chamber area, the arrangement of injection nozzles for a thorough and uniform mixing of the air with water vapor or water is achieved with difficulty only. Furthermore, there is the risk that critical thermoelectric voltages will be generated by the injected medium hitting the hot walls of the combustion chamber.
A gas turbine plant consisting of a compressor, a combustion chamber and a gas turbine, in which water or water vapor is fed onto the first row of turbine blades in the path of the combustion air behind the combustion chamber for increasing the efficiency, has become known from DE 102 05 972 A1.
A gas turbine plant, in which a heat exchanger is connected downstream of the gas turbine in the path of the exhaust gas for heating the combustion air compressed in the compressor of the gas turbine, has become known from JP 05332164 A. In order to increase the service life of the heat exchanger without compromising the heat utilization of the turbine exhaust gas, water or water vapor is fed into the compressed combustion air before its intake into the heat exchanger.